Polyethyleneimine polyethyleneglycol vectors

ABSTRACT

A polyplex of a double stranded RNA and a polymeric conjugate is provided, wherein the polymeric conjugate consists of a linear polyethyleneimine covalently linked to one or more polyethylene glycol (PEG) moieties, each PEG moiety being conjugated via a linker to a targeting moiety capable of binding to a cancer antigen.

FIELD OF INVENTION

The present invention relates to non-viral polyethylenimine-basedpolyplexes conjugated to a targeting moiety capable of binding to acancer antigen.

BACKGROUND OF THE INVENTION

One of the hurdles facing molecular medicine is the targeted delivery oftherapeutic agents such as DNA or RNA molecules. An emerging strategy isthe construction of non-viral vectors, such as cationic polymers andcationic lipids, which bind and condense nucleic acids. These non-viralcationic vectors possess many advantages over viral gene vectors, asthey are non-immunogenic, non-oncogenic and easy to synthesize [1-4].Currently, several synthetic polycationic polymers are being developedfor nucleic acid delivery. Among these, polyethylenimines (PEIs) areconsidered promising agents for gene delivery [5].

PEIs are water-soluble, organic macromolecules that are available asboth linear and branched structures [6]. PEIs change their degree ofionization over a broad range of pH, since every third atom in theirbackbone chain is an amino nitrogen, that can be protonated.Approximately 55% of the nitrogens in PEIs are protonated atphysiological pH [7]. They possess high cationic charge density, and aretherefore capable of forming non-covalent complexes with nucleic acids.Furthermore, their physicochemical and biological properties can bealtered by various chemical modifications [8]. PEI-based complexes (alsoknown as polyplexes) can be endocytosed by many cell types [9].Following internalization of the polyplexes, endosome release and highefficiency gene transfer are driven by the “proton sponge effect” [10].The ability of PEI to condense DNA appears to be an important factor indelivering large DNA constructs into many cell types.

The major concern in the utilization of PEIs as delivery carriers istoxicity, due to their high positive surface charge, which may lead tonon-specific binding [11]. Recent attempts have been made to improve theselectivity and biocompatibility of non-viral vectors. This has led tothe modification of PEI molecules with polyethylene glycol (PEG), inorder to shield the PEI particle [12]. The conjugation ofheterobifunctional PEG groups to PEI facilitates coupling of the PEI toa targeting ligand, which provides efficient gene delivery into cellsharboring the cognate receptor [12]. We have previously described thegeneration of targeting vectors, demonstrating the difference betweenbranched PEI (brPEI-EGF) and linear PEI (LPEI) tethered to EGF astargeting vectors [13, WO 2004/045491, WO 2010/073247]. Current methodsof synthesis are unsatisfactory in that they result in insufficientlyhomogeneous products. There is thus a pressing need for methods that canprovide efficient conjugation of targeting moieties to the LPEI-PEG in areproducible manner to produce homogenous batches of products that canbe reliably used in methods for treating cancer.

SUMMARY OF INVENTION

In one aspect, the present invention is related to a polyplex of adouble stranded RNA (dsRNA) and a polymeric conjugate, wherein saidpolymeric conjugate consists of a linear polyethyleneimine (LPEI)covalently linked to one or more polyethylene glycol (PEG) moieties,each PEG moiety being conjugated via a linker to a targeting moietycapable of binding to a cancer antigen, provided that the targetingmoiety is not mouse EGF (mEGF) or the peptide of the sequenceYHWYGYTPQNVI (GE11) (SEQ ID NO: 1).

In another aspect, the present invention provides a pharmaceuticalcomposition comprising a pharmaceutically acceptable carrier and apolyplex of the present invention as defined herein.

In yet another aspect, the present invention provides the polyplex ofthe present invention as defined herein, or the pharmaceuticalcomposition comprising the polyplex, for use in treatment of a cancerselected from a cancer characterized by EGFR-overexpressing cells, acancer characterized by HER2-overexpressing cells and prostate cancer.

In still another aspect, the present invention is related to a methodfor treating a cancer selected from the group consisting of a cancercharacterized by EGFR-overexpressing cells, a cancer characterized byHER2-overexpressing cells and prostate cancer, the method comprisingadministering to a subject in need a polyplex of the present inventionas defined herein.

In a further aspect, the present invention is related to apharmaceutical composition comprising a pharmaceutically acceptablecarrier and the polyplex of the present invention, for treatment of acancer selected from a cancer characterized by EGFR-overexpressingcells, a cancer characterized by HER2-overexpressing cells and prostatecancer.

The polyplex of the present invention may be used in combination withimmune cells.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows that conjugation of LPEI (˜22 kDa) with NHS-PEG-OPSS (˜2kDa) yielded mainly two co-polymeric networks that differ in the degreeof PEGylation. The co-polymer LPEI-(PEG_(2k)-OPSS)₃ (“di-conjugate 1:3”)consisted on average of 1 mole of LPEI and 3 moles of PEG, whereasco-polymer LPEI-PEG_(2k)-OPSS (“di-conjugate 1:1”), consisted on averageof 1 mole ratio of LPEI and 1 mole of PEG. (Ratios of LPEI:PEG weredetermined by ¹H-NMR analysis.)

FIG. 2 shows ¹H-NMR analysis of the two di-conjugates,LPEI-PEG_(2k)-OPSS (di-conjugate 1:1) and LPEI-(PEG_(2k)-OPSS)₃(di-conjugate 1:3). The coupling of PEG groups to LPEI was indicated bythe presence of the chemical shifts that correlate to ethylene glycolhydrogens (a) at 3.7 ppm and ethyleneimine hydrogens at ˜3.0 ppm (b).The integral values of these peaks provide molar ratios of PEG to LPEI,from which the illustrated structures of di-conjugate 1:1 (A) anddi-conjugate 1:3 (B) were deduced.

FIG. 3 shows a scheme for conjugation of the co-polymeric networks(di-conjugate 1:1 and di-conjugate 1:3) to the affibody (“Her-2”)through disulfide exchange, resulting in the generation of twodifferently PEGylated tri-conjugates [20].

FIG. 4 depicts an SDS/PAGE of purified affibody, di-conjugate andtri-conjugate, in the absence and in the presence of DTT. In thepresence of DTT, the affibody is released from the tri-conjugate, andmigrates alongside purified affibody (slightly above 10 kDa).

FIG. 5 shows particle sizing using DLS measurements of LPEI, thedi-conjugates and the tri-conjugates complexed with plasmid pGreenfire 1in HBG buffer pH 7.4.

FIG. 6 depicts ξ potential distributions of LPEI, di-conjugates andtri-conjugates complexed with plasmid pGreenfire1. The zeta potentialswere measured by DLS and calculated by the Smoluchowski equation.

FIGS. 7A-B show atomic force microscopy (AFM) images obtained frommeasurements performed in HBG buffer pH 7.4 for both polyplexes. (A)tri-conjugate 1:1 Polyplex (B) tri-conjugate 1:3 Polyplex. Scale bar is1 μm.

FIG. 8 depicts an agar gel showing that differentially PEGylatedpolyplexes protect plasmid pGreenFire1 from DNase I degradation. 1 μgplasmid (pGreenFire1) alone or in tri-conjugate polyplexes: 1:1 and 1:3was treated with or without DNase I (2 IU). Supercoiled plasmid (s.c.),open circular plasmid (o.c.).

FIGS. 9A-C show Her-2 mediated gene transfer of pGFP-LUC using thetri-conjugate 1:1 polyplex and the tri-conjugate 1:3 polyplex containingLPEI:PEG ratios of 1:1 and 1:3 respectively. 10000 BT474 and MDA-MB-231breast cancer cells/well were treated for 48 h with tri-conjugates 1:1and 1:3 complexed with pGFP-LUC (1 μg/ml) to generate the twopolyplexes. PEI nitrogen/DNA phosphate ratio of 6 (N/P=6) in HBS. (A)Measurements of luciferase activity demonstrate significant decreasedpGreenFire1 delivery in MDA-MB-231 cells, compared to BT474 and reducedgene delivery mediated by tri-conjugate 1:3 polyplexes as compared totri-conjugate 1:1 (* p<0.001). Luciferase activity was measured intriplicates after 48 h shown as relative lucifarese units (RLU) asmean+S.D. (B) Fluorescent images of cells treated with polyplexes.Images are shown at ×10 magnification and are representative of threeexperiments performed. (C) Methylene blue assay depicts percent of cellsurvival compared to untreated (UT) cells.

FIG. 10 shows that PEI-PEG-Her2Affibody (PPHA) complexed with PolyICinhibits Her2 overexpressing breast cancer cells BT474. The complexedvector inhibits Her2 overexpressing cells, includingHerceptin/trastusumab resistant cells.

FIG. 11 shows inhibition of MCF7 cells overexpressing Her2 injected innude mice.

FIGS. 12A-B shows the efficacy of (A) PEI-PEG-EGFRAffibody (PPEAffibody)in comparison to that of (B) PPE.

FIG. 13 shows the activity of PolyIC/PPEaffibody in vivo as comparedwith untreated (UT), pIC/PPE, pI/PPE, pI/PPEA and pIC/PPEA low (0.1μg/μl pIC in the complex).

FIG. 14 shows survival of U87MG, U87MGwtEGFR cells after application ofdifferent concentrations of PolyIC/LPEI-PEG-hEGF complex as comparedwith application of PolyIC/mPPE (mouse) as described in Schaffert D,Kiss M, Rödl W, Shir A, Levitzki A, Ogris M, Wagner E. (2011)Poly(I:C)-mediated tumor growth suppression in EGF-receptoroverexpressing tumors using EGF-polyethylene glycol-linearpolyethylenimine as carrier. Pharm Res. 28:731-41.

FIG. 15 shows that PEI-PEG (PP)-DUPA (PPD)/PolyIC is highly effectiveagainst LNCaP and VCaP cells. Viability was measured after 96 hr ofexposure.

FIGS. 16A-C shows production of the cytokines (A) IP-10, (B) Gro-α and(C) RANTES by LNCaP cell transfected with PolyIC/PPD.

FIGS. 17A-C shows that medium conditioned by LNCaP cells stimulatesexpression of cytokines in PBMCs. (A) Scheme showing the experimentalprocedure; (B) expression after 12 hrs incubation; and (C) expressionafter 24 hrs incubation.

FIG. 18 shows that co-incubation of PolyIC/PPD treated LNCaP cells withPC3-Luciferase cells which do not express PSMA, resulted in up to 70%killing of the PC3-Luciferase cells via bystander effect. Addition ofhealthy human PBMCs strongly enhanced the effect and lead to the killingof 90% of the PC3 cells.

FIG. 19 shows effect of PolyIC/PPD on subcutaneous LNCaP tumors in vivo.UT, untreated.

DETAILED DESCRIPTION OF THE INVENTION

Polycations, especially PEI, have been intensively investigated asagents for gene transfection. Optimal transfection efficacies areobtained when the polymeric nanoparticle complexes possess an overallpositive charge, which allows them to bind to the negatively chargedheparin sulfate proteoglycans on the cell surface [28]. Previous studiesshowed that linear PEI (LPEI) is more effective in gene transfectionthan branched PEI (brPEI) [29-31] [32, 33, WO 2010/073247], but thatLPEI has higher positive charge and hence is more toxic. Variousshielding entities, such as PEG [12], poly-(ethyleneoxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) [18, 34]and poly(ethylene oxide) [35], have been conjugated to cationicpolymers, in an attempt to lower the positive charge and the consequenttoxicity. Indeed, shielding of PEIs with PEG groups of varying lengthssignificantly lowered toxicity while maintaining transfection efficiency[12, 13, 36].

It has been found in accordance with the present invention that theconjugation of LPEI with PEG_(2k) yields di-conjugate co-polymerscomprising various ratios of LPEI to PEG_(2K). These di-conjugates couldbe separated from one another using cation exchange chromatography, dueto differences in charge, which reflect the different numbers ofPEG_(2k) groups conjugated. ¹H-NMR analysis confirmed that thedi-conjugates differed from one another in the average number ofPEG_(2k) units per LPEI unit, where di-conjugate 1:1 had an LPE:PEG_(2k)ratio of 1:1 and di-conjugate 1:3 had an LPE:PEG_(2k) ratio of 1:3. Theconjugation of the Her-2 targeting affibody to each of the purifieddi-conjugates yielded a tri-conjugate product of the appropriatemolecular weight, i.e. from di-conjugate 1:1 we obtained “tri-conjugate1:1” with LPE:PEG_(2k):Her-2 equal to 1:1:1 and from di-conjugate 1:3 weobtained “tri-conjugate 1:3”, with ratio 1:3:3. This protocol enabled usto obtain homogeneous products, with nearly complete conjugation oftargeting affibody to LPEI-PEG, in a reproducible manner.

We observed that PEGylation strongly affects the size of the polyplexparticles obtained upon complexation of the di-conjugates ortri-conjugates with plasmid DNA. Both di-conjugate 1:3 and tri-conjugate1:3 polyplexes had average particle sizes larger than di-conjugate 1:1and tri-conjugate 1:1 polyplexes. We believe that increasing the amountof PEGylation on a single cationic chain leads to steric hindrance,which prevents the polymeric chain from condensing the plasmid to asmaller particle. This is consistent with the finding that the nakedLPEI polyplex had the smallest particles. Moreover, while bothtri-conjugates 1:1 and 1:3 protected complexed plasmid from DNase I, thetri-conjugated 1:3 polyplex provided better protection, possibly due tothe increased steric hindrance.

Previous studies suggested that increasing the molecular weight of thePEG units conjugated to cationic polymers led to decreased surfacecharge of the polyplexes obtained upon complexation with nucleic acids[13]. Our data show that increasing the number of PEG groups of similarmolecular weights leads to decreased surface charge, as defined by ξpotential distribution. Indeed, the highest surface charge was shown bynaked LPEI complexed with plasmid. These results support the idea thatthe more neutral entities are present in a chemical vector, the lowerthe surface charge. Surprisingly, the tri-conjugate polyplexesconjugated to affibodies had lower surface charge than the di-conjugatepolyplexes, showing that the Her-2 affibody (which itself has slightpositive charge) also reduced the surface charge of the particles. Wesuspect that Her-2 affibody changes the topography of the particle withmore targeting moieties masking the charge on the surface, leading to adecrease in surface charge.

The shape of a polyplex has a significant effect on its performance as adrug delivery candidate [37, 38], although it is not yet known whichpolyplex shapes are desirable for effective drug delivery. The effect ofPEGylation on polyplex shape has not been investigated, to ourknowledge, until now. In AFM pictures, the tri-conjugate 1:1polyplex—which was more effective in gene delivery—presented shapehomogeneity, while the tri-conjugate 1:3 was more heterogenic, with manyasymmetrical, ellipsoidal particles.

Selective gene transfer using cationic polymers remains a majorchallenge. Previous studies have shown that targeting of LPEI andLPEI-PEG conjugates, with EGF or transferrin, increased theirselectivity and decreased non-specific interactions both in vitro and invivo [39, 40]. For example, to examine the selectivity of our Her-2targeting tri-conjugates 1:1 and 1:3 polyplexes, we utilized two breastcancer cells that differentially express Her-2. Gene delivery, as shownby luciferase activity and GFP expression, was significantly higher inBT474 cells, which highly overexpress the Her-2 receptor, than inMDA-MB-231 cells, which express 100-fold less Her-2 receptors on thecell surface. Thus, the data demonstrate that both tri-conjugates 1:1and 1:3 are highly selective for Her-2 overexpressing cells (FIG. 10).

Previous studies have shown that high levels of PEGylation can result inreduced gene transfection [41]. These results are in accordance with ourobservation that highly PEGylated tri-conjugate 1:3 polyplex showed asignificant reduction in gene delivery, as compared to the lessPEGylated tri-conjugate 1:1 polyplex, as shown by luciferase activityand GFP expression. The increased gene delivery by the lower PEGylatedtri-conjugate 1:1 polyplex was accompanied by slight cellular toxicity,most likely due to its higher surface charge.

Our working hypothesis before engaging in this study was that increasingthe number of targeting moieties per LPEI unit would lead to improvedgene delivery and/or selectivity. We speculated that tri-conjugate 1:3,which has 3 moles of Her-2 affibody molecules conjugated per mole ofLPEI, would show increased receptor-mediated particle internalization.However, the tri-conjugate 1:3 polyplexes showed lower ξ potential,larger particle size and heterogeneous, non-spherical shape, all ofwhich characteristics might contribute to the decreased transfectionefficiencies actually observed. Our results show that the less PEGylatedtri-conjugate 1:1 is superior to the more PEGylated tri-conjugate 1:3 inmediating selective and efficient gene delivery into Her-2overexpressing cells.

It has been found in accordance with the present invention thatPEGylation of LPEI-based polyplexes leads to decreased surface charge,increased polyplex size and increased shape heterogeneity, and thatthese properties can have profound effects on targeted gene delivery.Our simplified synthesis allows purification of homogeneous products ina reproducible fashion, which can now be expanded to generate differenttri-conjugates, using a variety of targeting moieties.

In view of the above, the present invention, in one aspect, provides apolyplex of a double stranded RNA (dsRNA) and a polymeric conjugate,wherein said polymeric conjugate consists of a linear polyethyleneimine(LPEI) covalently linked to one or more polyethylene glycol (PEG)moieties, each PEG moiety being conjugated via a linker to a targetingmoiety capable of binding to a cancer antigen, provided that thetargeting moiety is not mEGF or the peptide of the sequence YHWYGYTPQNVI(GE11) (SEQ ID NO: 1).

In certain embodiments, the cancer antigen may be, but is not limitedto, an epidermal growth factor receptor (EGFR), human epidermal growthfactor receptor 2 (HER2), prostate surface membrane antigen (PSMA), aninsulin-like growth factor 1 receptor (IGF1R), a vascular endothelialgrowth factor receptor (VEGFR), a platelet-derived growth factorreceptor (PDGFR) or a fibroblast growth factor receptor (FGFR). Thetargeting moiety may be a native, natural or modified ligand or aparalog thereof, or a non-native ligand such as an antibody, asingle-chain variable fragment (scFv), or an antibody mimetic such as anaffibody, to any one of the cancer antigens. Affibodies are based on theZ domain (the immunoglobulin G binding domain) of protein A and uniquebinding properties are acquired by randomization of 13 amino acidslocated in two alpha-helices involved in the binding activity of theparent protein domain.

In certain embodiments, the dsRNA is polyinosinic-polycytidylic aciddouble stranded RNA (poly I:C), the polymeric conjugate consists of LPEIcovalently linked to one PEG moiety (LPEI-PEG 1:1) or to three PEGmoieties (LPEI-PEG 1:3), and the cancer antigen is EGFR, HER2 or PSMA.

The molecular weight of PEG may be in the range of 2 to 8 kDa, inparticular 2 kDa; the molecular weight of LPEI may be in the range of 10to 30 kDa, in particular 22 kDa; and the polyIC of the polyplex of theinvention may be composed of RNA strands each comprising at least 22,preferably at least 45 ribonucleotides. In certain embodiments, eachstrand has a number of ribonucleotides within the range of 20 to 300.

In certain embodiments, the one or more PEG moieties each independentlyforms —NH—CO— bond with the LPEI and a bond selected from —NH—CO—,—CO—NH—, —S—C—, —S—S—, —O—CO— or —CO—O— with the linker. In particular,each one of the one or more PEG moieties forms —NH—CO— bonds with theLPEI and the linker.

In certain embodiments, the linker forms an —S—S—, NH—CO—, —CO—NH—,—S—C—, O—CO—, —CO—O— or urea (—NH—CO—NH) bond with the targeting moiety.The linker may be selected from —CO—R₂—R_(x)—R₃ or a peptide moietyconsisting of 3 to 7 amino acid residues, wherein

R₂ is selected from (C₁-C₈)alkylene, (C₂-C₈)alkenylene, (C₂-C₈)alkynylene, (C₆-C₁₀)arylene-diyl, or heteroarylenediyl;

R_(x) is absent or —S—;

R₃ is absent or of the formula

R₄ is selected from (C₁-C₈)alkylene, (C₂-C₈)alkenylene, (C₂-C₈)alkynylene, (C₁-C₈)alkylene-(C₃-C₈)cycloalkylene,(C₂-C₈)alkenylene-(C₃-C₈)cycloalkylene, (C₂-C₈)alkynylene-(C₃-C₈)cycloalkylene, (C₆-C₁₀)arylene-diyl,heteroarylenediyl, (C₁-C₈)alkylene-(C₆-C₁₀)arylene-diyl, or(C₁-C₈)alkylene-heteroarylenediyl;

wherein each one of said (C₁-C₈)alkylene, (C₂-C₈)alkenylene, or (C₂-C₈)alkynylene is optionally substituted by one or more groups eachindependently selected from halogen, —COR₅, —COOR₅, —OCOOR₅, —OCON(R₅)₂,—CN, —NO₂, —SR₅, —OR₅, —N(R₅)₂, —CON(R₅)₂, —SO₂R₅, —SO₃H, —S(═O)R₅,(C₆-C₁₀)aryl, (C₁-C₄)alkylene-(C₆-C₁₀)aryl, heteroaryl, or(C₁-C₄)alkylene-heteroaryl, and further optionally interrupted by one ormore identical or different heteroatoms selected from S, O or N, and/orat least one group each independently selected from —NH—CO—, —CO—NH—,—N(R₅)—, —N(C₆-C₁₀aryl)-, (C₆-C₁₀)arylene-diyl, or heteroarylenediyl;and

R₅ is H or (C₁-C₈)alkyl.

In certain embodiments, R₂ is selected from (C₁-C₈)alkylene, preferably(C₁-C₄)alkylene, optionally substituted by one or more groups eachindependently selected from halogen, —COH, —COOH, —OCOOH, —OCONH₂, —CN,—NO₂, —SH, —OH, —NH₂, —CONH₂, —SO₂H, —SO₃H, —S(═O)H, (C₆-C₁₀)aryl,(C₁-C₄)alkylene-(C₆-C₁₀)aryl, heteroaryl, or (C₁-C₄)alkylene-heteroaryl,and further optionally interrupted by one or more identical or differentheteroatoms selected from S, O or N, and/or at least one group eachindependently selected from —NH—CO—, —CO—NH—, —NH—, —N(C₁-C₈alkyl)-,—N(C₆-C₁₀aryl)-, (C₆-C₁₀)arylene-diyl, or heteroarylenediyl. Inparticular, R₂ is selected from (C₁-C₈)alkylene, preferably(C₁-C₄)alkylene.

In certain embodiments, R_(x) is —S—.

In certain embodiments, R₃ is absent or

wherein

R₄ is (C₁-C₈)alkylene-(C₃-C₈)cycloalkylene, preferably(C₁-C₄)alkylene-(C₅-C₆)cycloalkylene.

In certain embodiments, in the polyplex as defined above, R₂ is—CH₂—CH₂—; R_(x) is —S—; and R₃ is absent or

wherein R₄ is

In certain embodiments, the linker is a peptide moiety comprising atleast one, in particular two or three, aromatic amino acid residues suchas phenylalanine, tryptophan, tyrosine or homophenylalanine. In certainembodiments, the peptide moiety is—(NH—(CH₂)₇—CO)-Phe-Gly-Trp-Trp-Gly-Cys- (SEQ ID NO: 2) or—(NH—(CH₂)₇—CO)-Phe-Phe-(NH—CH₂—CH(NH₂)—CO)-Asp-Cys- (SEQ ID NO: 3),linked via its mercapto group to the targeting moiety.

In certain embodiments, the polymeric conjugate is a diconjugate of theformula (i)-(viii), linked to the targeting moiety/moieties:

In particular embodiments, the polyplex is selected from

(a) the polyplex, wherein the targeting moiety is HER2 affibody, and thepolymeric conjugate is of the formula (i) above, and the HER2 affibodyis linked via a mercapto group thereof, herein also referred to asLPEI-PEG_(2k)-HER2;

(b) the polyplex, wherein the targeting moiety is HER2 affibody, and thepolymeric conjugate is of the formula (v) above, and the HER2 affibodyis linked via a mercapto group thereof, herein also referred to asLPEI-(PEG_(2k)-HER2)₃;

(c) the polyplex, wherein the targeting moiety is EGFR affibody, and thepolymeric conjugate is of the formula (i) above, and the EGFR affibodyis linked via a mercapto group thereof, herein also referred to asLPEI-PEG_(2k)-EGFR;

(d) the polyplex, wherein the targeting moiety is EGFR affibody, and thepolymeric conjugate is of the formula (v) above, and the EGFR affibodyis linked via a mercapto group thereof, herein also referred to asLPEI-(PEG_(2k)-EGFR)₃;

(e) the polyplex, wherein the targeting moiety is human EGF (hEGF), andthe polymeric conjugate is of the formula (ii) above, wherein the hEGFis linked via an amino group thereof, herein also referred to asLPEI-PEG_(2k)-hEGF;

(f) the polyplex, wherein the targeting moiety is hEGF, and thepolymeric conjugate is of the formula (vi) above, wherein the hEGF islinked via an amino group thereof, herein also referred to asLPEI-(PEG_(2k)-hEGF)₃;

(g) the polyplex, wherein the targeting moiety isHOOC(CH₂)₂—CH(COOH)—NH—CO—NH—CH(COOH)—(CH₂)₂—CO— (DUPA residue), and thepolymeric conjugate is of the formula (iii) above;

(h) the polyplex, wherein the targeting moiety isHOOC(CH₂)₂—CH(COOH)—NH—CO—NH—CH(COOH)—(CH₂)₂—CO— (DUPA residue), and thepolymeric conjugate is of the formula (vii) above;

(i) the polyplex, wherein the targeting moiety isHOOC(CH₂)₂—CH(COOH)—NH—CO—NH—CH(COOH)—(CH₂)₂—CO— (DUPA residue), and thepolymeric conjugate is of the formula (iv) above; or

(j) the polyplex, wherein the targeting moiety isHOOC(CH₂)₂—CH(COOH)—NH—CO—NH—CH(COOH)—(CH₂)₂—CO— (DUPA residue), and thepolymeric conjugate is of the formula (viii) above.

The size of the nanoparticles formed by the polyplex of the presentinvention may be in the range of 120 to 150 nm, in particular 135-148nm, or 142 nm.

Non-limiting examples of procedures for the preparation of polymericconjugates used in the present invention are exemplified in Exampleshereinafter.

In certain particular embodiments, the EGFR affibody is of the aminoacid sequence as set forth in SEQ ID NO: 4, the HER2 affibody is of theamino acid sequence as set forth in SEQ ID NO: 5 and the hEGF is of theamino acid sequence as set forth in SEQ ID NO: 6.

In another aspect, the present invention relates to a pharmaceuticalcomposition comprising a pharmaceutically acceptable carrier and thepolyplex as defined above.

In yet another aspect, the present invention provides the polyplex ofthe present invention as defined herein, or the pharmaceuticalcomposition comprising the polyplex, for use in treatment of a cancerselected from a cancer characterized by EGFR-overexpressing cells, acancer characterized by HER2-overexpressing cells and prostate cancer.

In certain embodiments, the cancer characterized by EGFR-overexpressingcells is selected from non-small-cell-lung-carcinoma, breast cancer,glioblastoma, head and neck squamous cell carcinoma, colorectal cancer,adenocarcinoma, ovary cancer, bladder cancer or prostate cancer, andmetastases thereof. In certain embodiments, the polyplex used fortreatment of cancer characterized by EGFR-overexpressing cells isselected from the polyplex of (c), (d), (e) or (f) defined above.

In certain embodiments, the cancer characterized by HER2-overexpressingcells is selected from breast cancer, ovarian cancer, stomach cancer,and aggressive forms of uterine cancer, such as uterine serousendometrial carcinoma. In certain embodiments, the Her2 overexpressingcells are Herceptin/trastusumab resistant cells. Thus, the polyplex ofthe present invention may be for use in the treatment ofHerceptin/trastusumab resistant cancer, i.e. cancer comprising cellsthat do not respond, or respond to a lesser extent to exposure toHerceptin/trastusumab.

In particular, the polyplex used for treatment of cancer characterizedby HER2-overexpressing cells is selected from the polyplex (a), (b), (e)or (f) defined above.

In certain embodiments, the cancer is prostate cancer and the polyplexused for treatment of the prostate cancer is selected from (g), (h), (i)or (j) defined above.

In still another aspect the present invention is related to a method fortreating a cancer selected from the group consisting of a cancercharacterized by EGFR-overexpressing cells, a cancer characterized byHER2-overexpressing cells and prostate cancer, the method comprisingadministering to a subject in need a polyplex of the present inventionas defined herein.

In a further aspect the present invention is related to a pharmaceuticalcomposition comprising a pharmaceutically acceptable carrier and thepolyplex of the present invention, for treatment of a cancer selectedfrom a cancer characterized by EGFR-overexpressing cells, a cancercharacterized by HER2-overexpressing cells and prostate cancer.

In yet a further aspect, the present invention is directed to thepolyplex, the method, or the pharmaceutical composition of the presentinvention, for use in combination with immune cells.

In still a further aspect, the present invention is directed to apolyplex as defined herein above, in which the dsRNA is replaced with aDNA molecule, such as a plasmid comprising protein-encoding nucleic acidsequences operably linked to control elements such as appropriatepromoters and terminators.

In certain embodiments, the immune cells are tumor-infiltrating T-cells(T-TILs), tumor specific engineered T-cells, or peripheral bloodmononuclear cells (PBMCs).

The term “polyplex” as used herein refers to a complex between a nucleicacid and a polymer. The nucleic acid is bound to the polymer vianon-covalent or covalent bonds, in particular electrostatic bonds. Theterm “polyplex” refers to a vector, i.e. a non-viral vector, useful forcarrying and delivering nucleic acids into cells.

The term “patient”, “subject”, or “individual” are used interchangeablyand refer to either a human or a non-human animal.

The term “(C₁-C₈)alkyl”, as used herein, typically means a straight orbranched hydrocarbon radical having 1-8 carbon atoms and includes, e.g.,methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl,tert-butyl, n-pentyl, 2,2-dimethylpropyl, n-hexyl, n-heptyl, n-octyl,and the like.

The term “(C₁-C₈)alkylene” refers to a straight or branched divalenthydrocarbon radical having 1-8 carbon atoms and includes, e.g.,methylene, ethylene, propylene, butylene, pentanylene, hexanylene,heptanylene, octanylene, and the like. The term “(C₂-C₂)alkenylene” and“(C₂-C₈)alkynylene” typically mean straight or branched divalenthydrocarbon radicals having 2-8 carbon atoms and one or more double ortriple bonds, respectively. Non-limiting examples of such radicalsinclude ethenylene, propenylene, 1- and 2-butenylene, 1- and2-pentenylene, 1-, 2- and 3-hexenylene, 1-, 2- and 3-heptenylene, 1-,2-, 3- and 4-octenylene, ethynylene, propynylene, 1- and 2-butynylene,2-methylpropylene, 1- and 2-pentynylene, 2-methylbutylene, 1-, 2- and3-hexynylene, 1-, 2- and 3-heptynylene, 1-, 2-, 3- and 4-octynylene andthe like.

The term “(C₆-C₁₀)aryl” denotes an aromatic carbocyclic group having6-10 carbon atoms consisting of a single ring or condensed multiplerings such as, but not limited to, phenyl and naphthyl; the term“(C₆-C₁₀)arylene-diyl” denotes a divalent aromatic carbocyclic grouphaving 6-10 carbon atoms consisting of either a single ring or condensedmultiple rings such as, but not limited to, phenylene and naphthylene.

The term “heteroaryl” refers to a radical derived from a 5-10-memberedmono- or poly-cyclic heteroaromatic ring containing one to three,preferably 1-2, heteroatoms selected from N, O, or S. Examples ofmono-cyclic heteroaryls include, without being limited to, pyrrolyl,furyl, thienyl, thiazinyl, pyrazolyl, pyrazinyl, imidazolyl, oxazolyl,isoxazolyl, thiazolyl, isothiazolyl, pyridyl, pyrimidinyl,1,2,3-triazinyl, 1,3,4-triazinyl, and 1,3,5-triazinyl. Polycyclicheteroaryl radicals are preferably composed of two rings such as, butnot limited to, benzofuryl, isobenzofuryl, benzothienyl, indolyl,quinolinyl, isoquinolinyl, imidazo[1,2-c]pyridyl, benzimidazolyl,benzthiazolyl, benzoxazolyl, pyrido[1,2-a]pyrimidinyl and1,3-benzodioxinyl. The heteroaryl may optionally be substituted by oneor more groups each independently selected from halogen, —OH, —COOH,—CN, —NO₂, —SH, or —CONH₂. It is to be understood that when a polycyclicheteroaryl is substituted, the substitution may be in any of thecarbocyclic and/or heterocyclic rings. The term “heteroarylenediyl”denotes a divalent radical derived from a “heteroaryl” as defined hereinby removal of two hydrogen atoms from any of the ring atoms.

The term “halogen” as used herein refers to fluoro, chloro, bromo oriodo.

The term “(C₃-C₈)cycloalkylene” denotes a mono- or bi-cyclic saturateddivalent cyclic hydrocarbon radical containing three to eight carbons.Non-limiting examples of such radicals include 1,2-cyclopropane-diyl,1,2-cyclobutane-diyl, 1,3-cyclobutane-diyl, 1,2-cyclopentane-diyl,1,3-cyclopentane-diyl, 1,2-cyclohexane-diyl, 1,3-cyclohexane-diyl,1,4-cyclohexane-diyl, 1,2-cycloheptane-diyl, 1,3-cycloheptane-diyl,1,4-cycloheptane-diyl, 1,2-cyclooctane-diyl, 1,3-cyclooctane-diyl,1,4-cyclooctane-diyl, 1,5-cyclooctane-diyl, and the like.

The term “amino acid residue”, as used herein, refers to any natural orsynthetic, i.e., non-natural, amino acid residue in its both L- andD-stereoisomers. While a natural amino acid is any one of the twentyamino acid residues typically occurring in proteins, the termsynthetic/non-natural amino acid refers to any amino acid, modifiedamino acid and/or an analog thereof, that is not one of the twentynatural amino acids. Non-limiting examples of natural amino acidsinclude glycine, alanine, valine, leucine, isoleucine, lysine, valine,phenylalanine, glutamic acid, aspartic acid, asparagine, glutamine,arginine, histidine, proline, serine, tyrosine, methionine, threonine,and tryptophan. Examples of non-natural amino acids, without beinglimited to, include ornithine, homolysine, 2,4-diaminobutyric acid(DABA), 2,3-diaminopropionic acid (DAP), 8-aminooctanoic acid (EAO),homophenylalanine, homovaline, homoleucine, and the like.

Pharmaceutical compositions in accordance with the present invention maybe formulated in conventional manner using one or more physiologicallyacceptable carriers and/or excipients. The carrier(s) must be“acceptable” in the sense of being compatible with the other ingredientsof the composition and not deleterious to the recipient thereof.

The following exemplification of carriers, modes of administration,dosage forms, etc., are listed as known possibilities from which thecarriers, modes of administration, dosage forms, etc., may be selectedfor use with the present invention. Those of ordinary skill in the artwill understand, however, that any given formulation and mode ofadministration selected should first be tested to determine that itachieves the desired results.

Methods of administration include, but are not limited to, parenteral,e.g., intravenous, intraperitoneal, intramuscular, subcutaneous, mucosal(e.g., oral, intranasal, buccal, vaginal, rectal, intraocular),intrathecal, topical and intradermal routes. Administration can besystemic or local. In certain embodiments, the pharmaceuticalcomposition is adapted for intra-brain administration.

The term “carrier” refers to a diluent, adjuvant, excipient, or vehiclewith which the active agent is administered. The carriers in thepharmaceutical composition may comprise a binder, such asmicrocrystalline cellulose, polyvinylpyrrolidone (polyvidone orpovidone), gum tragacanth, gelatin, starch, lactose or lactosemonohydrate; a disintegrating agent, such as alginic acid, maize starchand the like; a lubricant or surfactant, such as magnesium stearate, orsodium lauryl sulphate; and a glidant, such as colloidal silicondioxide.

The compositions may be formulated for parenteral administration byinjection, e.g., by bolus injection or continuous infusion. Formulationsfor injection may be presented in unit dosage form, e.g., in ampoules orin multidose containers, with an added preservative. The compositionsmay take such forms as suspensions, solutions or emulsions in oily oraqueous vehicles, and may contain formulatory agents such as suspending,stabilizing and/or dispersing agents. Alternatively, the activeingredient may be in powder form for constitution with a suitablevehicle, e.g., sterile pyrogen free water, before use.

For administration by inhalation, for example for nasal administration,the compositions according to the present invention are convenientlydelivered in the form of an aerosol spray presentation from pressurizedpacks or a nebulizer, with the use of a suitable propellant, e.g.,dichlorodifluoromethane, trichlorofluoromethane,dichlorotetrafluoroethane, carbon dioxide or other suitable gas. In thecase of a pressurized aerosol the dosage unit may be determined byproviding a valve to deliver a metered amount. Capsules and cartridgesof, e.g., gelatin, for use in an inhaler or insufflator may beformulated containing a powder mix of the compound and a suitable powderbase such as lactose or starch.

In certain embodiments the pharmaceutical composition is formulated foradministration by any known method as described above. Particularmethods of administration contemplated here are intravenous andintra-brain (intracerebral) administration.

The pharmaceutical composition according to any one of the embodimentsdefined above may be formulated for intravenous, intra-brain(intracerebral), oral, intradermal, intramuscular, subcutaneous,transdermal, transmucosal, intranasal or intraocular administration.

The invention will now be illustrated by the following non-limitingExamples.

EXAMPLES Material and Methods (M&M) Chemicals

NHS-PEG-OPSS (Ortho-Pyridyldisulfide-Polyethyeneglycol-N-Hydroxylsuccinimide ester), also named PDP-PEG-NHS (PDP:pyridyl dithio propionate), with molecular weight of ˜2 kDa waspurchased from Creative PEGworks (Winston, USA). Poly(2-ethyl-2-oxazoline), average molecular weight (Mn) ˜50 kDa, andanhydrous dimethylsulfoxide (DMSO) were purchased from Sigma Aldrich(Israel). Absolute ethanol was purchased from Romical (Israel). Allsolvents were used without further purification.

Synthesis of ˜22 kDa LPEI (Free Base Form)

The cationic polymer Linear Polyethyleneimine (LPEI) was synthesized asdescribed previously [16]. Briefly, 8.0 g (0.16 mmols) ofpoly(2-ethyl-2-oxazoline) were hydrolyzed with 100 ml of concentratedHCl (37%) and refluxed for 48 h, yielding a white precipitate. ExcessHCl was removed under reduced pressure and the remaining solid wasdissolved in 50 ml of water and freeze-dried (5 g, 78%, ¹H-NMR, D₂O-d6,400 MHz: singlet 3.5 ppm). The resulting LPEI hydrochloride salt (4.5 g)was made alkaline by adding aqueous NaOH (3 M) and the resulting whiteprecipitate was filtrated and washed with water until neutral. The solidwas then dissolved in water and further lyophilized to give white solid(2 g, 81%).

Synthesis of LPEI-PEG_(2k)-OPSS Di-Conjugates

174 mg (8 μmol) of LPEI were dissolved in 2.7 ml of absolute EtOH andagitated at room temperature for 15 minutes. A 5-fold molar excess ofOPPS-PEG_(2k)-CONHS (79 mg, 39.5 μmol) was dissolved in 500 μL ofanhydrous DMSO and introduced in small portions into the LPEI mixture.The reaction mix was agitated at ˜800 rpm on a vortex stirrer at ambienttemperature for 3 h. Different PEG-substituted LPEIs were separated bycation-exchange chromatography, using an HR10/10 column filled withMacroPrep High S resin (BioRad). The purity of the eluted fractions ofthe di-conjugates was assessed using reverse phase HPLC equipped withanalytical Vydac C-8 monomeric 5 μm column (300 Å, 4.6×150 mm), using alinear gradient of 5%-95% acetonitrile over 25 min at 1 ml/min flow. Thefractions with 95% purity or higher were combined. The combinedfractions were further dialyzed against 20 mM HEPES pH 7.4. The ratio ofPEG_(2k) groups conjugated to LPEI in the di-conjugates was determinedby ¹H-NMR. The integral values of the hydrogens from the polyethylene—(CH₂—CH₂—O)— and from the LPEI —(CH₂—CH₂—NH)— were used to determinethe ratio between the two conjugated co-polymers. Of the variousproducts obtained from the cation-exchange, two products,LPEI-PEG_(2k)-OPSS (di-conjugate 1:1, with molar ration of LPEI to PEG˜1:1) and LPEI-(PEG_(2k))₃-(OPSS)₃ (di-conjugate 1:3, with molar ratioof ˜1:3), were chosen for the generation of tri-conjugates. A copperassay was used to evaluate the co-polymer concentration [17]. Briefly,co-polymers were incubated with CuSO₄ (23 mg dissolved in 100 ml ofacetate buffer) for 20 minutes and their absorbance at 285 nm wasmeasured.

SDS-Polyacrylamide Gel Electrophoresis (SDS-PAGE) of Proteins

Samples (30 μL) were diluted in SDS protein sample buffer with orwithout 100 mM DTT and then applied to Tricine gel (13% polyacrylamide).Electrophoresis was performed using cathode buffer (0.1 M Tris, 0.1 MTricine and 0.1% SDS pH 8.25) and anode buffer (0.21 M Tris pH 8.9) andprotein bands were visualized by staining with InstantBlue™.

Affibody Expression and Purification

A Her-2 affibody gene was cloned into plasmid pET28a, generating avector encoding Z:2891 affibody fused to an N-terminal hexahistidyl(His6) tag and a Cys residue at the C terminus. The affibody wasexpressed in E. coli BL21(DE3) as follows: The cells were grown at 37°C. to OD₆₀₀˜0.7. IPTG was added to a final concentration of 0.5 mM,followed by incubation at 30° C. for 4 h. The cell pellet was stored at−80° C. To purify the affibody, the cell pellet was resuspended inbuffer A (20 mM HEPES pH 7.4, 500 mM NaCl, 10% glycerol, 10 mM imidazoleand 2 mM β-mercaptoethanol) and disrupted using a MicrofluidizerProcessor M-110EHI according to the manufacturer's instructions. Thesoluble fraction was recovered by centrifugation at 12,000×g for 10 minat 4° C. The resulting fraction was loaded onto a Ni affinity column(Clontech, Mountain View, Calif.). Column was washed with buffer A for14 column volumes (cv). Thereafter, a step gradient elution wasperformed using increasing concentrations of buffer B (20 mM HEPES pH7.4, 500 mM NaCl, 10% glycerol, 500 mM Imidazole and 2 mMβ-Mercaptoethanol); 6% buffer B for 5 cv, 10% buffer B for 1.5 cv, 30%buffer B for 2 cv. The bound protein was eluted with 100% buffer B for 5cv (protein purification facility, Wolfson centre, Israel). The elutedfractions were then concentrated with an Amicon filter (3 kDa cutoff)and loaded onto Gel filtration column Superdex 30 prep grade (120 ml)(GE healthcare). The purified proteins were further analyzed by SDS-PAGEand confirmed using Western blot analysis with anti-affibody antibody(Abcam). The purity was further assessed by reverse phase HPLC(Merck-Hitachi model L-7100) as described previously.

Synthesis of PEI-PEG-Ligand Affibody (Tri-Conjugate 1:1 and 1:3)

4.97 mg of each di-conjugate (1:1 and 1:3) were dissolved in 940 μl 20mM HEPES pH 7.4. Then, 3.4 mg of Her-2 affibody in HBS were addeddropwise to the reaction. 4 ml of 20 mM HEPES plus 700 μL ofacetonitrile (HPLC Grade) were introduced to the reaction mix forincreased solubility. The reaction was further vortexed (800 rpm) atroom temperature until A₃₄₃ indicated complete turnover. The resultingtri-conjugates were purified by cation exchange chromatography on aHR10/10 column filled with MacroPrep High S resin (BioRad) (using threestep gradient elution of 20 mM HEPES pH 7.4 to 20 mM HEPES containing 3M NaCl). The eluted fractions were introduced to analytical RP-HPLC toassess the purity of tri-conjugates, fractions with 95% purity andhigher were combined and were kept at −80° C. The concentration of thetri-conjugate was determined by copper assay (as above). The amount ofconjugated protein was determined by A₂₈₀ using Nano-Drop 2000.

Verification and Purity of Chemical Vectors Conjugated to TargetingProtein.

The tri-conjugates were electrophoresed on SDS-PAGE, and stained withInstantBlue™, to confirm the conjugation of the affibody toLPEI-PEG_(2k). The purity of the tri-conjugates was confirmed by reversephase HPLC, using an analytical Vydac C-8 monomeric 5 μm column (300 Å,4.6×150 mm) at 1 ml/min while monitoring at 220 nm. A gradient elutionwith acetonitrile, 5%-95% in 25 min with triple distilled water (TDW)containing 0.1% TFA as mobile phase were used for the HPLC analysis.

Polyplex Formation

Plasmid pGreenFire1, encoding Firefly Luciferase and GFP (SystemBiosciences, Inc), was amplified in E. coli and purified by QiagenPlasmid Maxi Kits (Qiagen, Valencia, Calif., USA) according to themanufacturer's protocol. The tri-conjugate 1:1 or tri-conjugate 1:3 werecomplexed with plasmid at a ratio of N/P=6 in HEPES buffer glucose(where N=nitrogen from LPEI and P=phosphate from DNA) generating twoPolyplexes. To allow complete formation of the polyplexes particles, thesamples were incubated for 30 min at room temperature. The final plasmidconcentration in polyplexes samples was 100 μg/ml whereas for DNaseprotection assay and luciferase assay, the final concentration of theplasmid was 10 μg/ml.

ξ-Potential and Sizing Measurements

The sizes of the polyplex particles obtained after dispersal in HBGbuffer were measured at 25° C., by dynamic light scattering using aNano-ZS Zetasizer (Malvern, UK), using volume distribution calculation.The instrument is equipped with a 633 nm laser, and light scattering isdetected at 173° by back scattering technology (NIBS, Non-InvasiveBack-Scatter). Each sample was run in triplicate. ζ potentialmeasurements were also performed at 25° C. using a Nano-ZS Zetasizer(Malvern, UK). The ζ potential was evaluated after incubation ofpolyplexes in HBG buffer (pH 7.4). Light scattering from the movingparticles was detected at 17°, and the Smoluchowski Model was used todetermine the value of the Henry's function.

Atomic Force Microscopy

For AFM measurements, polyplexes were placed on freshly cleaved Micadisks (V1 12 mm, Ted Pella USA). Imaging was carried out in HBG bufferat 25° C., using commercial AFM, a NanoWizard® 3 (JPK instrument,Berlin, Germany) with QI™ mode. Si3N4 (MSNL-10 series, Bruker)cantilevers with spring constants ranging from 10 to 30 pN nm-1 werecalibrated by the thermal fluctuation method (included in the AFMsoftware) with an absolute uncertainty of approximately 10%. QI™settings were as follows: Z-length: 0.1 μm; applied force: 0.5 nN;speed: 50 μm/s.

DNase Protection Assay

DNase I protection assays were conducted as described previously [18].Briefly, 1 μg of pGreenFire1 DNA alone, with polyplex 1:1 or withpolyplex 1:3 was mixed in a final volume of 50 μl in HBS solution.Following 30 minutes incubation at room temperature, 2 μL of DNase I (2unit) or PBS were added to 10 μL of each sample and incubated for 15 minat 37° C. DNase I activity was terminated by the addition of 5 μL of 100mM EDTA for 10 min at room temperature. To dissociate the plasmid fromthe tri-conjugates, 10 μL of 5 mg/mL heparin (Sigma, St. Louis, Mo.)were added, and the tubes were incubated for 2 h at RT. Samples wereelectrophoresed on an 0.8% agarose gel and stained with ethidiumbromide. Images were acquired using a Gel Doc EZ Imager (Bio RadLaboratories, Inc).

Cell Culture

Her-2 overexpressing BT474 cells were cultured in RPMI mediumsupplemented with 10% fetal bovine serum (FBS), 10⁴ U/L penicillin, and10 mg/L streptomycin at 37° C. in 5% CO₂. MDA-MB-231 human breastcarcinoma cells, were cultured in Leibovitz L-15 medium with 10% FBS,10⁴ U/L penicillin, and 10 mg/L streptomycin at 37° C. without CO₂. Celllines were from the ATCC and cell culture reagents were from BiologicalIndustries, Bet Ha'emek, Israel.

Luciferase Assay and Confocal Microscopy

10000 BT474 and MDA-MB-231 cells were plated in triplicate in 96-wellplates. Cells were treated with tri-conjugate 1:1 and tri-conjugate 1:3complexed with plasmid 48 h following treatment, cells were washed withPBS and lysed with 30 μl of cell lysis buffer (Promega, Mannheim,Germany) per well. Luciferase activity was measured in 25 μl samples ofthe lysates, using the Luciferase Assay system (Promega) according tomanufacturer's recommendations. Measurements were performed using aLuminoskan™ Ascent Microplate Luminometer (Thermo Scientific). Values,in relative light units (RLU), are presented as the mean and standarddeviation of luciferase activity from the triplicate samples. Confocalmicroscopy (FV-1200 Olympus) was used to visualize the GFP, which wastaken to reflect the internalization of plasmid pGreenFire1. Pictureswere taken at ×10 magnification.

Quantification of Cell Viability

Cell viability was measured by means of a colorimetric assay usingmethylene blue, as described previously [19]. Briefly, 10000 BT474 andMDA-MB-231 cells were plated in triplicate in 96-well plates. The cellswere treated with polyplexes 1:1 and 1:3 containing 1 μg/ml pGreenFire1.48 h following treatment, the cells were fixed with 1% formaldehyde inPBS (pH 7.4), washed with DDW and then stained with a 1% (wt/vol)solution of methylene blue in borate buffer for 1 h. Thereafter, thestain was extracted with 0.1 M HCl and the optical density of the stainsolution was read at 630 nm in a microplate reader (ELx800 BIO-TEXinstruments Inc.).

Example 1 Synthesis of Thiol Reactive Co-Polymers

3.1. Previous studies have demonstrated the PEGylation of LPEI and itsconjugation to an EGFR targeting moiety [13]. However, the amount ofPEGylation on a single LPEI chain has not been fully characterized. Togenerate differentially PEGylated co-polymers, the secondary amines onLPEI were conjugated to the terminal NHS ester orthogonal protectinggroup on PEG. The N-hydroxysuccinimide (NHS) ester is spontaneouslyreactive with the secondary backbone amines of LPEI, providing efficientPEGylation of LPEI. Furthermore, the reaction of the NHS-PEG OPSS withthe amines of PEI results in formation of stable, irreversible amidebonds (FIG. 1).

The PEGylation products were purified by cation exchange chromatography.Two peaks were eluted at high concentrations of NaCl, one at 120 mS/cmand the other at 132 mS/cm (data not shown). The two products werepresumed to differ in their ratios of LPEI:PEG and consequently in theirnet positive charges. ¹H-NMR spectra were analyzed using the relativeintegral values of the hydrogen atoms on PEG (—CH₂—CH₂—O—) (FIG. 2) andthe integral values of the hydrogen atoms on LPEI (—CH₂—CH₂—NH—) (FIG.2). This analysis indicated that the material eluted in the first peakconsisted of a co-polymer in which each mole of LPEI was conjugated toapproximately three moles of PEG. This product was namedLPEI-(PEG_(2k))₃-(OPSS)₃ (“di-conjugate 1:3”). The second peak consistedof a co-polymer in which equal moles of PEG were conjugated to LPEI, andwas named LPEI-PEG_(2k)-OPSS (“di-conjugate 1:1”) (FIG. 2).

Example 2 Synthesis of the Tri-Conjugates, LPEI-PEG_(2k)-Her2 Affibody(Tri-Conjugate 1:1) & LPEI-(PEG_(2k))-(Her2)₃ Affibody (Tri-Conjugate1:3)

The primary aim of this study was to develop a cationic polymer thatwould target Her-2 overexpressing tumor cells. Since Her-2 is an “orphanreceptor”, affibody molecules targeting the Her-2 receptor (rather thanligand) were used to generate Her-2 targeting tri-conjugates. Weexpressed and purified Her-2 affibody with a Cys residue at theC-terminal end to allow further conjugation. The thiol reactiveco-polymers, di-conjugate 1:1 and 1:3, were conjugated to Her-2 affibodythrough its terminal Cys residue, generating tri-conjugates 1:1 and 1:3respectively (FIG. 3). In order to generate the tri-conjugates thereaction had to be performed with low concentration of affibody (toprevent aggregation) and in the presence of 10% acetonitrile (ACN) as anorganic polar solvent for increased solubility. The reaction yields forboth tri-conjugate reactions were approximately 33% as determined bycopper assay. To confirm the conjugation of the affibody to thedi-conjugate, the tri-conjugate products were reduced with DTT andseparated on SDS-PAGE. Coomassie blue staining confirmed that thereduced tri-conjugate released the affibody (FIG. 4). The amount ofHer-2 affibody present in the tri-conjugates was determined by measuringA₂₈₀. Using copper assay, we quantified the LPEI. As described above,¹H-NMR analysis showed that the ratios of LPEI:PEG in the purifieddi-conjugates were 1:1 or 1:3. Comparing the molar ratios of Her-2affibody and LPEI, we determined that the average ratio of Her-2affibody to LPEI in tri-conjugate 1:1 was 1:1, and in tri-conjugate 1:3the average ratio was 3:1. Thus we conclude that nearly completeconjugation of affibody to LPEI-PEG was achieved.

To generate polyplexes, the pure di-conjugates and tri-conjugates (1:1and 1:3) were complexed with plasmid DNA, as described in the Materialsand Methods (FIG. 3).

Example 3 ξ Potential and Sizing of Polyplexes

We next characterized the polyplexes, with respect to size and surfacecharge, using dynamic light scattering (DLS). The size of a polyplex hasa significant impact on its delivery properties [21]. In order toinvestigate the effect of targeting ligand on the size of a polyplex wedecided to complex both di-conjugates 1:1 and 1:3 with plasmid andmeasure their size. Di-conjugate 1:1 had an average particle size of115.2±8.2 nm and di-conjugate 1:3 had an average particle size of253.1±9.5 nm. The polyplex generated from tri-conjugate 1:1 with plasmidgave an average particle size of 141±5.8 nm, whereas tri-conjugate 1:3complexed with plasmid had an average particle size of 256±24.2 nm (FIG.5). The smallest particles (73.9±3.0 nm) were obtained in polyplexesgenerated by complexing the plasmid with LPEI alone. The conjugation ofthe affibody to the di-conjugates had only a minor affect on theparticle size. The number of PEG groups, however, did affect theparticle size, suggesting that the PEG groups cause steric hindrance,interfering with plasmid condensation.

A positive surface charge facilitates polyplex binding to the negativelycharged cell surface, but excessive positive charge can lead tonon-specific binding and significant toxicity [12]. The ξ potentials ofthe various complexes, presented in FIG. 6, are in agreement withprevious studies, which showed a decrease in ξ potential with increasednumber of PEG units [13]. To assess the effect of PEG groups on thesurface charge of our chemical vectors we measured the ξ potentials ofpolyplexes formed by complexation of plasmid DNA with the precursors,di-conjugates 1:1 and 1:3, and with the tri-conjugates 1:1 and 1:3.Di-conjugate polyplex 1:1 had an average ξ potential of 27.0±0.1 mV anddi-conjugate polyplex 1:3 had an average ξ potential of 20.0±1.0 mV.Tri-conjugate polyplex 1:1 showed ξ potential with an average of17.1±0.7 mV, whereas tri-conjugate polyplex 1:3 showed an average of10.2±0.44 mV (FIG. 6). Unlike the sizes, the ξ potentials of thepolyplexes were affected by both the number of PEG groups and theconjugation of the Her-2 affibody. Although the smallest, mostpositively charged polyplexes were obtained with naked LPEI, theseparticles are extremely toxic [22]. We expected that the addition of PEGgroups and a targeting moiety would diminish toxicity, but because thepolyplexes were still relatively small in size, we hoped that theirefficiency as nucleic acid delivery vectors would not be compromised.

Example 4 Assessment of Polyplex Shape Using Atomic Force Microscopy

The importance of particle shape and its influence on deliveryproperties is gaining recognition [23]. We analyzed the morphology ofthe polyplexes obtained with the tri-conjugates in solution using AtomicForce Microscopy (AFM). The diameters of tri-conjugates 1:1 and 1:3polyplexes were both in the nano-size range (FIGS. 7A-B), in agreementwith the results obtained by DLS. The tri-conjugate 1:1 polyplexdisplayed mainly elliptical particles. Most particles ranged in diameterfrom 101 nm to 178 nm, with an average particle diameter of 142 nm. Afew particles were exceptionally large, with some even reaching >250 nm(FIG. 7A). Tri-conjugate 1:3 polyplex was more heterogenic in shape, andmoreover, yielded large aggregates with undefined particle shape (FIG.7B). These ranged in length from 150 nm to 650 nm, with an averageparticle length of 312 nm and their width ranged from 85 nm to 400 nm,with an average width of 175 nm.

Example 5 DNAse Protection Assay

Successful in vivo gene delivery depends on efficient protection fromnucleases. To determine the ability of the tri-conjugates to protectplasmids from degradation and enable efficient gene delivery, thepolyplexes were treated with DNase I and analyzed using gelelectrophoresis. As shown in FIG. 8, naked plasmid pGreenFire1 DNA wasfully degraded following 10 minutes of incubation with 2 units of DNaseI. In contrast, when polyplexes were generated by mixing plasmid withthe tri-conjugates, the plasmid was protected from degradation by DNaseI. Complete protection of the plasmid was observed for tri-conjugatepolyplex 1:3, while some nicking did occur for tri-conjugate polyplex1:1, as shown by the shift from the supercoiled (s.c.) to the opencircular (o.c.) form of the plasmid. The stronger protection from DNaseI conferred by tri-conjugate polyplex 1:3 may be attributed to theincreased steric hindrance provided by the additional PEG-protein unitsin these complexes. Indeed, previous studies have shown that PEGylationof PEI can stabilize polyplexes and increase their circulation in theblood, by impeding their interactions with enzymes and serum factors[24, 25].

Example 6 Biological Activity of Targeting Tri-Conjugate Polyplexes

Polyplex size and ξ potential influence the efficiency of targeted DNAdelivery and gene expression, but the effect of size appears to bedependent on the particular conjugate [2] [21]. To evaluate thespecificity and the efficiency of transfection of the tri-conjugatepolyplexes 1:1 and 1:3, two breast cancer cell lines that differentiallyexpress Her-2 were utilized. Polyplexes of the tri-conjugates 1:1 and1:3 were formed with pGreenFire1 and transfected into MDA-MB-231 cells(expressing approximately 9×10³ Her-2 receptors/cell [26]) and BT474cells (expressing approximately 1×10⁶Her-2 receptors/cell [27]).Differential luciferase activity was observed 48 h after transfection.Both tri-conjugate polyplexes 1:1 and 1:3 led to more than 300-foldhigher luciferase activity in BT474 cells than in MDA-MB-231 (* p<0.001)(Figure. 9A). More efficient gene delivery to BT474 was confirmed by GFPexpression, as seen by confocal microscopy (FIG. 9B). These results showthat polyplex selectivity is dependent on Her-2 expression.

Targeted delivery to BT474 cells by tri-conjugate polyplex 1:1 was10-fold more efficient than delivery by tri-conjugate polyplex 1:3 (FIG.9A, B), even though tri-conjugate 1:3 has more targeting moieties. Thismay reflect the higher ξ potential and lower size of tri-conjugatepolyplex 1:1.

Positively charged LPEI-based chemical vectors are associated withsignificant toxicity. Therefore, we next tested the survival ofMDA-MB-231 and BT474 cells following treatment with tri-conjugatepolyplexes 1:1 and 1:3. Neither polyplex showed cytotoxic effects inMDA-MB-231 cells, in a methylene blue assay. Similar results wereobserved in BT474 cells treated with tri-conjugate polyplex 1:3.However, a slight increase in cell cytoxicity was observed in BT474treated with tri-conjugate polyplex 1:1 (FIG. 9C). Altogether, theseresults indicate that the small size and higher ξ potential oftri-conjugate polyplex 1:1 confer efficient targeted deliveryproperties, with only a slight increase in toxicity. Thus, polyplex ofthe tri-conjugate 1:1 is superior in gene delivery to the more shieldedtri-conjugate polyplex 1:3.

Example 7 Anti-Tumor Activity of PEI-PEG-Her2Affibody

The PEI-PEG-Her2Affibody (PPHA) complexed with Polylnosine/PolyCytosine(PolyIC) has strong anti-tumor activity. Breast cancer cell linesoverexpressing Her-2 were found to be strongly inhibited by a complex ofPEI-PEG-Her2Affibody with PolyIC. Strong inhibition was observed also oftrastuzumab resistant Her2 overexpressing breast cancer cell lines.

FIG. 10 shows that the vector/polyplex inhibits Her2 overexpressingcells, including Herceptin/trastusumab resistant cells.

0.5×10⁶ MCF-7 HER-2 cells were injected s.c. into nude mice. Aftertumors reached and average of 100 mm³, treatment began. 1 mg/kg pIC/PPHAwas injected i.v. at every 24 hrs. Trastuzumab was administered i.v.once a week (indicated by arrows), to two groups of mice. Tumor growthwas measured twice a week. The complex PolyIC/PPHA was found to possessstrong anti-tumor activity in mouse models in which these cell lineswere implanted in nude mice as exemplified in FIG. 11.

Example 8 Synthesis of LPEI-PEG-EGFR Affibody

5 mg (2×10⁻⁴ mmol) of LPEI-PEG_(2k)-OPSS (di-conjugate 1:1) weredissolved in 1 ml 20 mM HEPES pH 7.4. Then, 3.4 mg (3.8×10⁻⁴ mmol, ˜2eq) of EGFR affibody in HBS were added dropwise to the reaction. 4 ml of20 mM HEPES plus 700 μL of acetonitrile (HPLC Grade) were introduced tothe reaction mix for increased solubility. The reaction was furthervortexed (800 rpm) at room temperature and dark conditions until A₃₄₃indicated complete turnover. The resulting tri-conjugate was purified bycation exchange chromatography on a HR10/10 column filled with MacroPrepHigh S resin (BioRad) (using three step gradient elution of 20 mM HEPESpH 7.4 to 20 mM HEPES containing 3 M NaCl). The eluted fractions wereintroduced to analytical RP-HPLC to assess the purity of LPEI-PEG-EGFRtri-conjugate, fractions with 95% purity and higher were combined andwere kept at −80° C. The concentration of the tri-conjugate wasdetermined by copper assay. The amount of conjugated protein wasdetermined by A₂₈₀ using Nano-Drop 2000.

Example 9 Anti-Tumor Activity of PEI-PEG-EGFR Affibody

The PEI-PEG-EGFRAffibody (PPEA) complexed with PolyIC has stronganti-tumor activity. A variety cell lines overexpressing EGFR were foundto be strongly inhibited by a complex of PEI-PEG-EGFRAffibody (PPEA) incomplex with Polylnosine/PolyCytosine (PolyIC). It can be seen that theefficacy of PPEA is higher than that of PPE (FIG. 12).

The complex PolyIC/PPEA was found to possess strong anti-tumor activityin mouse models in which these cell lines were implanted in nude mice.

Sixty five female nude mice 5 weeks old were injected s.c. with 2million A431 cells. Seven days later tumors of average volume of 136 mm³had grown and mice were divided into 6 groups (7-8 mice/group) asfollows: UT; pIC/PPEA, 0.75 mg/kg=250 μl of pIC for 25 gr mouse, IC,6/week; pI/PPEA, 0.75 mg/kg IV, 6/week; pIC/PPEA low, 0.1 mg/kg=250 μlof 0.01 μg/μl pf pIC for 25 gr mouse IC, 6/week. pIC, pI and PPE andPPEA were diluted before mixing to obtain lower than ususal (0.1 μg/μl)concentration of pIC in the complex. FIG. 13 shows the activity ofPolyIC/PPEffibody in vivo. Again, the efficacy of PPEA/PolyIC is higherthan that of PolyIC/PPE.

Example 10 Synthesis of LPEI-PEG-h/mEGF 10.1. Synthesis of LPEI-PEG-SHIntermediate

To 5 mg of LPEI-PEG-OPSS (0.2 mol, according to 24000 g/mol) in 5 ml of20 mM HEPES (pH 7.4) buffer was added 50-fold molar excess ofdithiothreitol (DTT; 0.1 mmol, 1.5 mg) and mixed by vortex for 20 min atroom temperature in 15 ml plastic centrifugation tube. The reduceddiconjugate was separated on Sephadex G-25 column (20 ml, 4×5 ml) using5 ml sample loop and the elution performed with 20 mM HEPES, pH 7.4 at1.0 ml/min flow rate and were analyzed by HPLC using the same conditionsand method as described above.

Ellman's assay was used to evaluate the sulfhydryl group concentrationin the LPEI-PEG-SH intermediate. The concentration of SH groups isdirectly proportional to the concentration of chromophor6-nitro-3-thioxocyclohexa-1,4-diene-1-carboxylic acid, released by freethiols that react quantitatively with Ellman's reagent. The chromophorwas measured via absorbance at 412 nm, without any interference from thesample or the Ellman's reagent.

10.2 Synthesis of m/hEGF-MCC Intermediate

Synthesis Outline.

The h/mEGF (human/mouse Epidermal Growth Factor) was modified intoh/mEGF-MCC (EGF-4-(N-Maleimidomethyl)cyclohexane-1-carboxylic acid; MCC)and purified to be later used for the conjugation with the LPEI-PEG-SH.Activating h/mEGF by attaching the MCC group circumvents reduction ofthe protein by DTT and allows to avoid exposure of h/mEGF to harshconditions. This way the conjugation reaction efficiency is improved,moreover—EGF-MCC is a stable material that can be stored at −80° C. forweeks.

Synthesis of hEGF-MCC:

1 mg of hEGF (160 nmol) was reconstituted in 0.5 ml water then degassedwith argon. The amount of hEGF was determined at 280 nm using nano-drop2000. The solution was added to 0.5 ml of 200 mM sodium acetate bufferpH 6.0, and 60% ethanol while mixing vigorously. The solution was mixedwith 10 equivalents of 4-(N-maleimidomethyl)cyclohexane-1-carboxylicacid 3-sulfo-N-hydroxysuccinimide ester sodium salt (Sulfo-SMCC) in 0.5ml of 100% ethanol under argon. The slightly acidic pH of the reactionmixture (pH 6) was necessary to selectively modify the N-terminal aminogroup of hEGF. After 4 h at room temperature, the functionalized peptidewas purified by dialysis bags (3.5 k cutoff) against HBS (100 mM), threetimes in 1 L for 1 hour, then 1 L for overnight. The hEGF-MCC wasanalyzed using HPLC-mass spectra (MS) and had a molecular weight of6435.7 g/mol, which indicates there is one conjugation of sulfo-SMCC tothe hEGF. The HPLC-MS analysis was performed using Thermo SCIENTIFIC/LCQFLEET, equipped with reverse phase C-18 column (phenomenex, Aeris, 3.6μm, 2.1 mm×50 mm, 100 A°).

Synthesis of mEGF-MCC:

0.5 mg (0.088 μmol total amount) of Murine EGF (PeproTech) was dissolvedin 2100 μL of 20 mM HEPES buffer forming a clear viscous solution. Onemg of sulfo-SMCC (30 eq., Ornat, Ill.) was dissolved in 0.9 mL absoluteEtOH and slowly mixed with EGF solution to reach the final concentrationof 30% EtOH in total 3.0 ml volume. Brief mixing resulted in a clearsolution. The reaction vessel was shaken at ambient temperature for 4hours. After that period of time the solution remained clear. ThemEGF-MCC was first separated on Sephadex G-25 column (4×5 ml) and theelution performed with 20 mM HEPES, pH 7.4 at 1.0 ml/min flow rate andfurther purified and analyzed by HPLC using the same conditions andstandard method as described above for LPEI-PEG-OPSS.

10.3 Synthesis of LPEI-PEG-h/mEGF

One and a half of equivalents of hEGF-MCC or mEGF-MCC were mixed with1.0 equivalent of LPEI-PEG-SH. The reaction mixture was initiallyagitated at room temperature for 2 hours, and then incubated for 4 daysat +4° C. with slow shaking. The reaction product (LPEI-PEG-hEGF orLPEI-PEG-mEGF) was separated by cation-exchange chromatography (7.8 cmMacroPrep High S resin (BioRad) in 10/1 cm Tricorn GE Healthcare column)using the gradient pump via A18 buffer inlet, at 0.5 ml/min flow rateand using solvent A: 20 mM HEPES pH 7.4 and solvent B: 20 mM HEPES pH7.4 NaCl 3.0 M. The purified LPEI-PEG-hEGF or LPEI-PEG-mEGF triconjugatewas analyzed by HPLC and quantified by a “copper assay” and an EGFphotometric assay to measure [LPEI] and [EGF] concentrations,correspondingly.

10.4 Biological Activity of LPEI-PEG-hEGF.

Using the cellular assay we usually employ we compared the activity ofthe PolyIC/LPEI-PEG-hEGF complex (PPEm) with the PolyIC/mPPE (mouse)described in Schaffert D, Kiss M, Rödl W, Shir A, Levitzki A, Ogris M,Wagner E., 2011 (Poly(I:C)-mediated tumor growth suppression inEGF-receptor overexpressing tumors using EGF-polyethylene glycol-linearpolyethylenimine as carrier. Pharm Res. 28:731-41). It can be seen thatthe new HEGF conjugate is more effective in killing EGFR over-expressingcells (FIG. 14). Cells that express moderate amounts of EGFR moleculeson their surface (U87MG cells express 80,000 EGFRs/cell) are lesssensitive to the treatment than cells over-expressing massive amounts(U87MGwtEGFR cells express 1,000,000 EGFRs/cell).

Example 11 Synthesis of DUPA Analog-DyLight 680

The peptide was synthesized using standard Fmoc solid-phase peptidesynthesis (SPPS) procedures on Fmoc-Cys(trt) wang resin as the solidsupport. Swelling: the resin was swelled for at least 2 h indichloromethane. Fmoc removal: the resin was first treated with asolution of 20% piperidine in dimethylformamide (DMF) (2×20 min), thenwashed with DMF (5×2 min). Coupling of Fmoc-Asp(OtBu)-OH: 3 eq. ofFmoc-Asp(OtBu)-OH, 3 eq. of(1-[bis(dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium3-oxid hexafluorophosphate) (HATU) were dissolved in 15 ml of DMF and 8eq. of N,N-diisopropylethylamine (DIEA or DIPEA) were added to themixture. The solution was mixed (pre-activated) for 10 minutes at roomtemperature before it was added to the resin for 1 hour. The couplingwas repeated twice with the new mixture in order to ensure completecoupling of aspartic acid. A Keiser test was performed to ensure acomplete coupling. The resin was washed with DMF (3×2 minutes) anddichloromethane (DCM) (2×2 min). Capping: The resin was treated with asolution of acetic anhydride (10 eq.) and DIPEA (8 eq.) in DMF for 20min and washed with DMF (3×2 min). Fmoc removal: The resin was firsttreated with a solution of 20% piperidine in DMF (2×20 min), then washedwith DMF (5×2 min). Coupling of Fmoc-diaminopropionic (DAP) acid: 3 eq.of Fmoc-diaminopropionic (DAP) acid, 3 eq. of HATU and 8 eq. of DIEAwere dissolved in 15 ml of DMF. The solution was mixed (pre-activated)for 10 minutes at room temperature before it was added to the resin for1 hour. A Keiser test was performed to ensure a complete coupling. Theresin was washed with DMF (3×2 minutes) and DCM (2×2 min). Peptideelongation: the following compounds were coupled to the resin in thefollowing order (1) Fmoc-Phe-OH, (2) Fmoc-Phe-OH, (3)Fmoc-8-aminooctanoic (EAO) acid, and (4) OtBu-Glu(Fmoc)-OH. Fmocremoval: the resin was treated with a solution of 20% piperidine in DMF(2×20 min), then washed with DMF (5×2 min) and DCM (3×2 min). Couplingof the DUPA ligand: (19 mL of triethylamine (6.6 mmol) was combined with0.9 gr (3 mmol) of L-glutamic acid di-tertbutyl ester hydrochloride in15 mL DCM. This solution was added dropwise over 45 minutes to asolution of 5 mL DCM and triphosgene (0.35 g, 1.1 mmol) at 0° C. Afterstirring for additional 5 min the mixture was added to the resin withadditional 0.9 mL of triethylamine. The reaction mixture with the resinwas shaked for 3 hours and washed with DMF (3×2 min). Full Cleavage: theresin was washed with DCM (3×2 min) and dried under vacuum. A solutionof 2.5% TDW and 2.5% triisopropylsilane in trifluoroacetic acid (TFA) at0° C. was added. The reaction proceeded for 4 h at room temperature,filtered and treated with a cooled solution of ether/hexane 1:1, and thepeptides were precipitated by centrifugation. The crude peptides weredissolved in acetonitrile/TDW 1:1 solution and lyophilized. The crudewas purified by preparative reverse phase (RP) HPLC. DyLight 680Coupling: under argon atmosphere, 1 mg of DyLight™ 680 (LifeTechnologies, Cat. No. 46418) was dissolved in anhydrous dimethylsulfoxide (DMSO; 100 μL) containing 50 equivalents of anhydrousdiisopropylethylamine. A two-fold molar excess of a DUPA peptide linkerdissolved in anhydrous DMSO (100 μL) was added to the above mixture andstirred at room temperature. The formations of products were confirmedby liquid chromatography-mass spectrometry (LC-MS). The crude DUPAnear-infrared (NIR) probes were then purified by preparative RP-HPLC.

Example 12 Synthesis of Dupa Analog-Drug Lead

The peptide was synthesized using standard Fmoc SPPS procedures onFmoc-Cys(trt) wang resin as the solid support. Swelling: the resin wasswelled for at least 2 h in dichloromethane. Fmoc removal: the resin wastreated with a solution of 20% piperidine in DMF (2×20 min), then washedwith DMF (5×2 min). Coupling of Fmoc-Gly-OH: 3 eq. of Fmoc-Gly-OH, and 3eq. of HATU were dissolved in 15 ml of DMF, followed by addition of 8eq. of DIEA. The solution was mixed (pre-activated) for 10 minutes atroom temperature before it was added to the resin for 1 hour. Thecoupling was repeated twice with the new mixture. A Keiser test wasperformed to ensure a complete coupling. The resin was washed with DMF(3×2 minutes) and DCM (2×2 min). Capping: The resin was treated with asolution of acetic anhydride (10 eq.) and DIPEA (8 eq.) in DMF for 20min and washed with DMF (3×2 min). Fmoc removal: the resin was treatedwith a solution of 20% piperidine in DMF (2×20 min), then washed withDMF (5×2 min). Coupling of Fmoc-Trp(Boc)-OH: 3 eq. of theFmoc-Trp(Boc)-OH, 3 eq. of HATU and 8 eq. of DIEA were dissolved in 15ml DMF. The solution was mixed (pre-activated) for 10 minutes at roomtemperature before it was added to the resin for 1 hour. A Keiser testwas performed to ensure a complete coupling. The resin was washed withDMF (3×2 min) and DCM (2×2 min). Peptide elongation: the followingcompounds were coupled to the resin in the following order (1)Fmoc-Trp(Boc)-OH, (2) Fmoc-Gly-OH, (3) Fmoc-Phe-OH, (4)Fmoc-8-aminooctanoic(EAO) acid, and (5) OtBu-Glu(Fmoc)-OH. Fmoc removal:the resin was treated with a solution of 20% piperidine in DMF (2×20min), then washed with DMF (5×2 min) and DCM (3×2 min). Coupling of theDUPA ligand: 0.9 mL of triethylamine (6.6 mmol) was combined with 0.9 gr(3 mmol) of L-glutamic acid di-tertbutyl ester hydrochloride in 15 mLDOA This solution was added dropwise over 45 minutes to a solution of 5mL DCM and triphosgene (0.35 g, 1.1 mmol) at 0° C. After stirring foradditional 50 min the mixture was added to the resin with additional 0.9mL of triethylamine. The reaction mixture with the resin was shaked for3 hours and washed with DMF (3×2 min). Full Cleavage: the resin waswashed with DCM (3×2 min) and dried under vacuum. A solution of 2.5% TDWand 2.5% triisopropylsilane in trifluoroacetic acid (TFA) at 0° C. wasadded. The reaction proceeded for 4 h at room temperature, filtered andtreated with a cooled solution of ether/hexane 1:1, and the peptidescontaining the DUPA analog were precipitated by centrifugation. Thecrude peptides were dissolved in acetonitrile/TDW 1:1 solution andlyophilized. The crude was purified by preparative RP-HPLC. Synthesis ofPEI-PEG-DUPA analog: 4.37 mg (1.2×10⁻⁴ mmol) of di-conjugate 1:1 or 1:3(prepared as explained in Example 1 herein above) were dissolved in 940μl of 20 mM HEPES pH 7.4. Then, 1 mg (9.1×10⁻⁴ mmol, ˜5 eq) of the DUPAanalog, was dissolved in 2 ml of acetonitrile (ACN; HPLC grade)/(20 mMHEPES pH 7.4) at a ratio of 1:1, were added dropwise to the reaction.Then, to reach an approximate ˜10% total concentration of ACN in thereaction, an addition of 4 mL of 20 mM were introduced into the reactionmixture. The reaction was further vortexed (800 rpm) in the dark at roomtemperature until the absorption at wavelength 343 (A₃₄₃) indicated acomplete turnover. The resulting tri-conjugate was purified by cationexchange chromatography on a HR10/10 column filled with MacroPrep High Sresin (BioRad) (using a three-step gradient elution of 20 mM HEPES pH7.4 to 20 mM HEPES containing 3 M NaCl). The eluted fractions wereintroduced to an analytical RP-HPLC to assess the purity of thetri-conjugate. Fractions with 95% purity and higher were combined andwere kept at −80° C. The concentration of the tri-conjugate wasdetermined by the copper assay. The amount of conjugated DUPA analog wasdetermined by the chromophores' (Trp amino acid) absorption.

Example 13 PolyIC/LPEI-PEG-DUPA Targets Prostate Cancer

Prostate surface membrane antigen (PSMA) is overexpressed in metastaticprostate cancer. It is also found in the neovasculature of most solidtumors. Since PSMA is internalized upon ligand binding we have chosen itas a target, design and synthesize a PolyIC PSMA targeting vector.Indeed, DUPA-Daylight680 is internalized to PSMA overexpressing cells(LNCaP) but not to MCF7 (overexpressing Her2) (not shown).

FIG. 15 shows that PEI-PEG-DUPA (PPD)/PolyIC is highly effective againstLNCaP and VCaP cells. Viability was measured after 96 hr of exposure.PPD also induces the production of cytokines (FIG. 16). In FIG. 17, itis demonstrated that medium conditioned by LNCaP cells stimulatesexpression of the cytokines INF-γ, IL-2 and TNF-α in PBMCs grown in theconditioned medium. It was then shown that co-incubation of PolyIC/PPDtreated LNCaP cells with PC3-Luciferase cells which do not express PSMA,resulted in up to 70% killing of the PC3-Luciferase cells via bystandereffect. Addition of healthy human PBMCs strongly enhanced the effect andlead to the killing of 90% of the PC3 cells (FIG. 18).

Example 14 Cancer Treatment In Vivo

PolyIC/PPD has significant anti-tumor effects when tested in SCID mice(FIG. 19). Tumor inhibition is not complete due to the lack of immunesystem in the experimental mice.

REFERENCES

-   1. Boussif, O., et al., A versatile vector for gene and    oligonucleotide transfer into cells in culture and in vivo:    polyethylenimine. Proc Natl Acad Sci USA, 1995. 92(16): p. 7297-301.-   2. Wagner, E., et al., Transferrin-polycation-DNA complexes: the    effect of polycations on the structure of the complex and DNA    delivery to cells. Proc Natl Acad Sci USA, 1991. 88(10): p. 4255-9.-   3. Little, S. R., et al., Poly-beta amino ester-containing    microparticles enhance the activity of nonviral genetic vaccines.    Proc Natl Acad Sci USA, 2004. 101(26): p. 9534-9.-   4. Davis, M. E., Z. G. Chen, and D. M. Shin, Nanoparticle    therapeutics: an emerging treatment modality for cancer. Nat Rev    Drug Discov, 2008. 7(9): p. 771-82.-   5. Remy, J. S., et al., Targeted gene transfer into hepatoma cells    with lipopolyamine-condensed DNA particles presenting galactose    ligands: a stage toward artificial viruses. Proc Natl Acad Sci    USA, 1995. 92(5): p. 1744-8.-   6. Jager, M., et al., Branched and linear poly(ethylene imine)-based    conjugates: synthetic modification, characterization, and    application. Chem Soc Rev, 2012. 41(13): p. 4755-67.-   7. Ziebarth, J. D. and Y. Wang, Understanding the protonation    behavior of linear polyethylenimine in solutions through Monte Carlo    simulations. Biomacromolecules, 2010. 11(1): p. 29-38.-   8. Hobel, S., et al., Maltose- and maltotriose-modified,    hyperbranched poly(ethylene imine)s (0M-PEIs): Physicochemical and    biological properties of DNA and siRNA complexes. J Control    Release, 2011. 149(2): p. 146-58.-   9. Rejman, J., A. Bragonzi, and M. Conese, Role of clathrin- and    caveolae-mediated endocytosis in gene transfer mediated by lipo- and    polyplexes. Mol Ther, 2005. 12(3): p. 468-74.-   10. Behr, J. P., The proton sponge: A trick to enter cells the    viruses did not exploit. Chimia, 1997. 51(1-2): p. 34-36.-   11. Suh, J., H. J. Paik, and B. K. Hwang, Ionization of    Poly(Ethylenimine) and Poly(Allylamine) at Various Phs. Bioorganic    Chemistry, 1994. 22(3): p. 318-327.-   12. Ogris, M., et al., PEGylated DNA/transferrin-PEI complexes:    reduced interaction with blood components, extended circulation in    blood and potential for systemic gene delivery. Gene Ther, 1999.    6(4): p. 595-605.-   13. Schaffert, D., et al., Poly(I:C)-mediated tumor growth    suppression in EGF-receptor overexpressing tumors using    EGF-polyethylene glycol-linear polyethylenimine as carrier. Pharm    Res, 2011. 28(4): p. 731-41.-   14. Nilsson, B., et al., A synthetic IgG-binding domain based on    staphylococcal protein A. Protein Eng, 1987. 1(2): p. 107-13.-   15. Lofblom, J., et al., Affibody molecules: engineered proteins for    therapeutic, diagnostic and biotechnological applications. FEBS    Lett, 2010. 584(12): p. 2670-80.-   16. Brissault, B., et al., Synthesis, characterization, and gene    transfer application of poly(ethylene glycol-b-ethylenimine) with    high molar mass polyamine block. Biomacromolecules, 2006. 7(10): p.    2863-70.-   17. Ungaro, F., et al., Spectrophotometric determination of    polyethylenimine in the presence of an oligonucleotide for the    characterization of controlled release formulations. J Pharm Biomed    Anal, 2003. 31(1): p. 143-9.-   18. Gebhart, C. L., et al., Design and formulation of polyplexes    based on pluronic-polyethyleneimine conjugates for gene transfer.    Bioconjug Chem, 2002. 13(5): p. 937-44.-   19. Dent, M. F., et al., The methylene blue colorimetric microassay    for determining cell line response to growth factors.    Cytotechnology, 1995. 17(1): p. 27-33.-   20. Eigenbrot, C., et al., Structural basis for high-affinity HER2    receptor binding by an engineered protein. Proc Natl Acad Sci    USA, 2010. 107(34): p. 15039-44.-   21. Ogris, M., et al., The size of DNA/transferrin-PEI complexes is    an important factor for gene expression in cultured cells. Gene    Ther, 1998. 5(10): p. 1425-33.-   22. Chollet, P., et al., Side-effects of a systemic injection of    linear polyethylenimine-DNA complexes. J Gene Med, 2002. 4(1): p.    84-91.-   23. Champion, J. A., Y. K. Katare, and S. Mitragotri, Particle    shape: A new design parameter for micro- and nanoscale drug delivery    carriers. Journal of Controlled Release, 2007. 121(1-2): p. 3-9.-   24. Kleemann, E., et al., Nano-carriers for DNA delivery to the lung    based upon a TAT-derived peptide covalently coupled to PEG-PEI. J    Control Release, 2005. 109(1-3): p. 299-316.-   25. Rudolph, C., et al., Nonviral gene delivery to the lung with    copolymer-protected and transferrin-modified polyethylenimine.    Biochim Biophys Acta, 2002. 1573(1): p. 75-83.-   26. Aguilar, Z., et al., Biologic effects of heregulin/neu    differentiation factor on normal and malignant human breast and    ovarian epithelial cells. Oncogene, 1999. 18(44): p. 6050-62.-   27. Park, J. W., et al., Anti-HER2 immunoliposomes: enhanced    efficacy attributable to targeted delivery. Clin Cancer Res, 2002.    8(4): p. 1172-81.-   28. Rabenstein, D. L., Heparin and heparan sulfate: structure and    function. Nat Prod Rep, 2002. 19(3): p. 312-31.-   29. Seib, F. P., A. T. Jones, and R. Duncan, Comparison of the    endocytic properties of linear and branched PEIs, and cationic PAMAM    dendrimers in B16f10 melanoma cells. J Control Release, 2007.    117(3): p. 291-300.-   30. Jeong, G. J., et al., Biodistribution and tissue expression    kinetics of plasmid DNA complexed with polyethylenimines of    different molecular weight and structure. J Control Release, 2007.    118(1): p. 118-25.-   31. Kawakami, S., et al., Evaluation of proinflammatory cytokine    production induced by linear and branched polyethylenimine/plasmid    DNA complexes in mice. J Pharmacol Exp Ther, 2006. 317(3): p.    1382-90.-   32. Goula, D., et al., Polyethylenimine-based intravenous delivery    of transgenes to mouse lung. Gene Ther, 1998. 5(9): p. 1291-5.-   33. Bragonzi, A., et al., Comparison between cationic polymers and    lipids in mediating systemic gene delivery to the lungs. Gene    Ther, 1999. 6(12): p. 1995-2004.-   34. Lee, K., et al., Pluronic/polyethylenimine shell crosslinked    nanocapsules with embedded magnetite nanocrystals for magnetically    triggered delivery of siRNA. Macromol Biosci, 2010. 10(3): p.    239-45.-   35. Zheng, M., et al., Poly(ethylene oxide) grafted with short    polyethylenimine gives DNA polyplexes with superior colloidal    stability, low cytotoxicity, and potent in vitro gene transfection    under serum conditions. Biomacromolecules, 2012. 13(3): p. 881-8.-   36. Petersen, H., et al., Polyethylenimine-graft-poly(ethylene    glycol) copolymers: influence of copolymer block structure on DNA    complexation and biological activities as gene delivery system.    Bioconjug Chem, 2002. 13(4): p. 845-54.-   37. Champion, J. A., Y. K. Katare, and S. Mitragotri, Particle    shape: a new design parameter for micro- and nanoscale drug delivery    carriers. J Control Release, 2007. 121(1-2): p. 3-9.-   38. Liu, Y., et al., The shape of things to come: importance of    design in nanotechnology for drug delivery. Ther Deliv, 2012.    3(2): p. 181-94.-   39. Kloeckner, J., et al., Photochemically enhanced gene delivery of    EGF receptor-targeted DNA polyplexes. J Drug Target, 2004. 12(4): p.    205-13.-   40. Kircheis, R., et al., Polyethylenimine/DNA complexes shielded by    transferrin target gene expression to tumors after systemic    application. Gene Ther, 2001. 8(1): p. 28-40.-   41. Ogris, M., et al., DNA/polyethylenimine transfection particles:    influence of ligands, polymer size, and PEGylation on    internalization and gene expression. AAPS PharmSci, 2001. 3(3): p.    E21.

1. A polyplex of a double stranded RNA (dsRNA) and a polymericconjugate, wherein said polymeric conjugate consists of a linearpolyethyleneimine (LPEI) covalently linked to one or more polyethyleneglycol (PEG) moieties, each PEG moiety being conjugated via a linker toa targeting moiety capable of binding to a cancer antigen, provided thatthe targeting moiety is not mouse EGF or the peptide of the sequenceYHWYGYTPQNVI (GE11) (SEQ ID NO: 1).
 2. The polyplex of claim 1, whereinthe dsRNA is polyinosinic-polycytidylic acid double stranded RNA (polyI:C), the polymeric conjugate consists of LPEI covalently linked to onePEG moiety (LPEI-PEG 1:1) or to three PEG moieties (LPEI-PEG 1:3), andthe cancer antigen is epidermal growth factor receptor (EGFR), humanepidermal growth factor receptor 2 (HER2) or prostate surface membraneantigen (PSMA).
 3. The polyplex of claim 1, wherein said one or more PEGmoieties each independently forms —NH—CO— bond with said LPEI and a bondselected from —NH—CO—, —CO—NH—, —S—C—, —S—S—, —O—CO— or —CO—O— with saidlinker.
 4. The polyplex of claim 3, wherein each one of said one or morePEG moieties forms —NH—CO— bonds with said LPEI and said linker.
 5. Thepolyplex of claim 1, wherein said linker forms an —S—S—, NH—CO—,—CO—NH—, —S—C—, O—CO—, —CO—O— or urea (—NH—CO—NH) bond with saidtargeting moiety.
 6. The polyplex of claim 5, wherein said linker isselected from —CO—R₂—R_(x)—R₃ or a peptide moiety consisting of 3 to 7amino acid residues, wherein R₂ is selected from (C₁-C₈)alkylene,(C₂-C₈)alkenylene, (C₂-C₈) alkynylene, (C₆-C₁₀)arylene-diyl, orheteroarylenediyl; R_(x) is absent or —S—; R₃ is absent or of theformula

R₄ is selected from (C₁-C₈)alkylene, (C₂-C₈)alkenylene, (C₂-C₈)alkynylene, (C₁-C₈)alkylene-(C₃-C₈)cycloalkylene,(C₂-C₈)alkenylene-(C₃-C₈)cycloalkylene, (C₂-C₈)alkynylene-(C₃-C₈)cycloalkylene, (C₆-C₁₀) arylene-diyl,heteroarylenediyl, (C₁-C₈)alkylene-(C₆-C₁₀)arylene-diyl, or(C₁-C₈)alkylene-heteroarylenediyl; wherein each one of said(C₁-C₈)alkylene, (C₂-C₈)alkenylene, or (C₂-C₈) alkynylene is optionallysubstituted by one or more groups each independently selected fromhalogen, —COR₅, —COOR₅, —OCOOR₅, —OCON(R₅)₂, —CN, —NO₂, —SR₅, —OR₅,—N(R₅)₂, —CON(R₅)₂, —SO₂R₅, —SO₃H, —S(═O)R₅, (C₆-C₁₀)aryl,(C₁-C₄)alkylene-(C₆-C₁₀)aryl, heteroaryl, or (C1-C4)alkylene-heteroaryl,and further optionally interrupted by one or more identical or differentheteroatoms selected from S, O or N, and/or at least one group eachindependently selected from —NH—CO—, —CO—NH—, —N(R₅)—, —N(C₆-C₁₀aryl)-,(C₆-C₁₀)arylene-diyl, or heteroarylenediyl; and R₅ is H or (C₁-C₈)alkyl.7. The polyplex of claim 6, wherein R₂ is selected from (C₁-C₈)alkylene,preferably (C₁-C₄)alkylene, optionally substituted by one or more groupseach independently selected from halogen, —COH, —COOH, —OCOOH, —OCONH₂,—CN, —NO₂, —SH, —OH, —NH₂, —CONH₂, —SO₂H, —SO₃H, —S(═O)H, (C₆-C₁₀)aryl,(C₁-C₄)alkylene-(C₆-C₁₀)aryl, heteroaryl, or (C₁-C₄)alkylene-heteroaryl,and further optionally interrupted by one or more identical or differentheteroatoms selected from S, O or N, and/or at least one group eachindependently selected from —NH—CO—, —CO—NH—, —NH—, —N(C₁-C₈alkyl)-,—N(C₆-C₁₀aryl)-, (C₆-C₁₀)arylene-diyl, or heteroarylenediyl.
 8. Thepolyplex of claim 7, wherein R₂ is selected from (C₁-C₈)alkylene,preferably (C₁-C₄)alkylene.
 9. The polyplex of claim 6, wherein R_(x) is—S—.
 10. The polyplex of claim 6, wherein R₃ is absent or

wherein R₄ is (C₁-C₈)alkylene-(C₃-C₈)cycloalkylene, preferably(C₁-C₄)alkylene-(C₅-C₆)cycloalkylene.
 11. The polyplex of claim 10,wherein R₂ is —CH₂—CH₂—; R_(x) is —S—; and R₃ is absent or

wherein R₄ is


12. The polyplex of claim 6, wherein said peptide moiety is—(NH—(CH₂)₇—CO)-Phe-Gly-Trp-Trp-Gly-Cys- (SEQ ID NO: 2) or—(NH—(CH₂)₇—CO)-Phe-Phe-(NH—CH₂—CH(NH₂)—CO)-Asp-Cys- (SEQ ID NO: 3),linked via its mercapto group to said targeting moiety.
 13. The polyplexof claim 1, wherein the polymeric conjugate is a diconjugate of theformula (i)-(viii), linked to said targeting moiety/moieties:


14. The polyplex of claim 13, wherein (a) said targeting moiety is HER2affibody, and said polymeric conjugate is of the formula 13(i), and theHER2 affibody is linked via a mercapto group thereof; (b) said targetingmoiety is HER2 affibody, and said polymeric conjugate is of the formula13(v), and the HER2 affibody is linked via a mercapto group thereof; (c)said targeting moiety is EGFR affibody, and said polymeric conjugate isof the formula 13(i), and the EGFR affibody is linked via a mercaptogroup thereof; (d) said targeting moiety is EGFR affibody, and saidpolymeric conjugate is of the formula 13(v), and the EGFR affibody islinked via a mercapto group thereof; (e) said targeting moiety is hEGF,and said polymeric conjugate is of the formula 13(ii), wherein the hEGFis linked via an amino group thereof; (f) said targeting moiety is hEGF,and said polymeric conjugate is of the formula 13(vi), wherein the hEGFis linked via an amino group thereof; (g) said targeting moiety isHOOC(CH₂)₂—CH(COOH)—NH—CO—NH—CH(COOH)—(CH₂)₂—CO— (DUPA residue), andsaid polymeric conjugate is of the formula 13(iii); (h) said targetingmoiety is HOOC(CH₂)₂—CH(COOH)—NH—CO—NH—CH(COOH)—(CH₂)₂—CO— (DUPAresidue), and said polymeric conjugate is of the formula 13(vii); (i)said targeting moiety isHOOC(CH₂)₂—CH(COOH)—NH—CO—NH—CH(COOH)—(CH₂)₂—CO— (DUPA residue), andsaid polymeric conjugate is of the formula 13(iv); or (j) said targetingmoiety is HOOC(CH₂)₂—CH(COOH)—NH—CO—NH—CH(COOH)—(CH₂)₂—CO— (DUPAresidue), and said polymeric conjugate is of the formula 13(viii). 15.The polyplex of claim 14, wherein said EGFR affibody is of the aminoacid sequence as set forth in SEQ ID NO: 4 and said HER2 affibody is ofthe amino acid sequence as set forth in SEQ ID NO:
 5. 16. Apharmaceutical composition comprising a pharmaceutically acceptablecarrier and a polyplex of claim
 1. 17. (canceled)
 18. The method ofclaim 24, wherein said cancer characterized by EGFR-overexpressing cellsis selected from non-small-cell-lung-carcinoma, breast cancer,glioblastoma, head and neck squamous cell carcinoma, colorectal cancer,adenocarcinoma, ovary cancer, bladder cancer or prostate cancer, andmetastases thereof.
 19. The method of claim 18, wherein said polyplex isselected from the group consisting of a polyplex in which: (c) saidtargeting moiety is EGFR affibody, and said polymeric conjugate is ofthe formula 13(i), and the EGFR affibody is linked via a mercapto groupthereof; (d) said targeting moiety is EGFR affibody, and said polymericconjugate is of the formula 13(v), and the EGFR affibody is linked via amercapto group thereof; (e) said targeting moiety is hEGF, and saidpolymeric conjugate is of the formula 13(ii), wherein the hEGF is linkedvia an amino group thereof; and (f) said targeting moiety is hEGF, andsaid polymeric conjugate is of the formula 13(vi), wherein the hEGF islinked via an amino group thereof.
 20. The method of claim 24, whereinsaid cancer characterized by HER2-overexpressing cells is selected frombreast cancer, ovarian cancer, stomach cancer, and aggressive forms ofuterine cancer, such as uterine serous endometrial carcinoma.
 21. Themethod of claim 20, wherein said cancer characterized byHER2-overexpressing cells is Herceptin/trastusumab resistant cancer. 22.The method of claim 20, wherein said polyplex is selected from the groupconsisting of a polyplex in which: (a) said targeting moiety is HER2affibody, and said polymeric conjugate is of the formula 13(i), and theHER2 affibody is linked via a mercapto group thereof; (b) said targetingmoiety is HER2 affibody, and said polymeric conjugate is of the formula13(v), and the HER2 affibody is linked via a mercapto group thereof; (e)said targeting moiety is hEGF, and said polymeric conjugate is of theformula 13(ii), wherein the hEGF is linked via an amino group thereof;and (f) said targeting moiety is hEGF, and said polymeric conjugate isof the formula 13(vi), wherein the hEGF is linked via an amino groupthereof.
 23. The method of claim 24, wherein said cancer is prostatecancer and said polyplex is selected from the group consisting of apolyplex in which: (g) said targeting moiety isHOOC(CH₂)₂—CH(COOH)—NH—CO—NH—CH(COOH)—(CH₂)₂—CO— (DUPA residue), andsaid polymeric conjugate is—(NH—(CH₂)₇—CO)-Phe-Phe-(NH—CH₂—CH(NH₂)—CO)-Asp-Cys-PEG_(2k)-LPEI; (h)said targeting moiety isHOOC(CH₂)₂—CH(COOH)—NH—CO—NH—CH(COOH)—(CH₂)₂—CO— (DUPA residue), andsaid polymeric conjugate is

(i) said targeting moiety isHOOC(CH₂)₂—CH(COOH)—NH—CO—NH—CH(COOH)—(CH₂)₂—CO— (DUPA residue), andsaid polymeric conjugate is—(NH—(CH₂)₇—CO)-Phe-Gly-Trp-Trp-Gly-Cys-PEG_(2k)-LPEI; and (j) saidtargeting moiety is HOOC(CH₂)₂—CH(COOH)—NH—CO—NH—CH(COOH)—(CH₂)₂—CO—(DUPA residue), and said polymeric conjugate is


24. A method for treating a cancer selected from the group consisting ofa cancer characterized by EGFR-overexpressing cells, a cancercharacterized by HER2-overexpressing cells and prostate cancer, saidmethod comprising administering to a subject in need thereof a polyplexaccording to claim
 1. 25. (canceled)
 26. The method of claim 24, whereinthe polyplex is administered in combination with immune cells.
 27. Themethod of claim 26, wherein said immune cells are tumor-infiltratingT-cells (T-TILs), tumor specific engineered T-cells, or peripheral bloodmononuclear cells (PBMCs).